Just wondered what ratio of petrol to 2-stroke oil is appropriate on the new model bikes. Is it 20:1?

Thanks

No, If you're using a good quality synthetic 40:1 (25 cc per litre) or 50:1 (20 cc per litre), I used to use Castrol A747 (excellent semi syth at 40:1) when I was racing 2 smokes (now a confirmed deisel man):D . BTW steer away from silkolene as in the words of a well known TT mechanic " I wouldn't use that in my lawn mower"